The purpose of this project is to develop methods for the extraction, isolation, and characterization of polypeptides with the property of conferring the transformed phenotype on normal indicator cells. These purified transforming growth factors (TGFs) will then form the basis for investigation of the mechanism of transformation and more specifically for the development of protein antagonists to these TGFs. Central to the investigation is the purification and characterization of the sarcoma growth factors (SGFs) found upon direct extraction of murine-sarcoma virus transformed cells grown in culture. Once isolated, the generality of this SGF will then be investigated by comparing its properties to those of TGFs isolated from a variety of tumor cells of non-viral origin, as well as to those of polypeptides with similar characteristics isolated from normal mouse tissues.